Abstract

Trees incorporated into urban environments have both ecological and social values which help sustain public health and well being. What is not known is how resilient urban trees are to the challenges, including climate change, of the 21st century. If the species composition of trees in urban environments is likely to change over time then this raises questions about the effects on the ecosystem services provided. The aims of this research are to examine the relationship between trees and their role within urban environments, and to critically review the external forces that are likely to cause change. In Runcorn, a town in northwest England, large scale landscaping and tree planting that built on the existing topography and vegetation was an integral part of the town’s spatial planning strategy. This planting took place between 1960 and the 1980s. The trees within these vegetated areas have reached maturity and questions are being asked about their future. In this paper the authors discuss the current floral composition of this element of Runcorn’s green infrastructure and consider the affect of predicted climate change. Species lists and abundance data have been combined with the 2009 UK climate projections to produce tree landscape change scenarios to circa 2080. At present there are twenty seven tree species in Runcorn. Ecological Site Classification (ESC) has been used to predict future suitability for tree species within Runcorn. Results relating to the seven species presented in this paper suggest that the trees and woodlands within Runcorn are going to be altered significantly. The east of Runcorn is considered to have ideal conditions for Betula pendula, Alnus glutinosa, Fagus sylvatica, Quercus robur and Prunus avium. However, climate change predictions suggest that by the 2080 the location where these species are expected to thrive is going to reduce and relocate to the west. These species contribute 34% of the overall tree abundance and are widely distributed around Runcorn. This shift in species distribution across Runcorn and the reduction in the number of species present will have an effect on the value of green spaces to other wildlife across Runcorn. According to Southwood (1961) and Rose and harding (1978) Quercus robur has the highest number of associated insect (284) and lichen (324) species of any tree and shrub species. Other species such as Betula pendula and Alnus glutinosa also rank highly with regard to the number of associated insect (229-90) and lichen (126-105) species. Whereas Fraxinus excelsior ranks significantly lower in terms of associated insect species and have only 41. Therefore, the changes in the tree communities across Runcorn could lead to a reduced number of invertebrate fauna and as a result, could affect the number of avian fauna. With a change in tree species distribution predicted across the town land owners will need to consider implementing a strategy to deal with these changes. The paper concludes with a description of future work that will assess current management practices and measure the ecosystem services attributed to Runcorn’s urban trees.